Forty-three studies met the inclusion criteria. Seven studies were included in the meta-analyses of RCTs: 4 investigated hypothesis one (n=302) and 3 investigated hypothesis two (n=665). Eleven studies were included in the meta-analyses of non-RCTs: 9 investigated hypothesis one (n=20,364) and 2 investigated hypothesis two (n=1,575). Twenty-five studies were included in a narrative synthesis. These comprised 19 case series, (2 looking at open-Hasson access (n=2,506), 9 looking at closed-needle/trocar access (n=80,885) and 8 looking at closed-direct/trocar access (n=19,740)); 4 abstracts (3 non-English language (n=3,434) and 1 grey-literature (n=2,975)); one historically controlled trial (n=300) relevant to the first hypothesis; and one cohort study (n=100) relevant to the second hypothesis.
'Visual/open' versus 'blind/closed' access.
Four RCTs (quality score: 16 to 24), 9 non-RCTs (quality score: 11 to 20) and one historically controlled trial (quality score 12) not included in the meta-analyses looked at open versus needle/trocar access. Further information was also provided by 8 case series (2 of open access and 6 of needle/troca access). None of the included studies looked at open versus direct trocar access.
Safety: studies contributing data on major complications showed both clinical and statistical heterogeneity (chi-squared 11.12, d.f.=5, P=0.049). Stratification showed possible differences relating to patient selection. Non-randomised prospective studies on patients with similar levels of prior abdominal surgery in both groups indicated a trend towards a reduced risk of major complications during open access (RR 0.30, 95% CI: 0.09, 1.03). Open access was also associated with a trend towards a reduced risk of access-site herniation (RR 0.21, 95% CI: 0.04, 1.03) and, in non-obese patients, a 57% reduction in minor complications (RR 0.43, 95% CI: 0.04, 1.17). The risk of bowel injury was higher with open access than with needle/trocar access (RR 2.17, 95% CI: 1.14, 4.10), although selection bias may have influenced the results.
Efficacy: pooled estimates from RCTs showed that both the total time to establish pneumoperitoneum (WMD -0.78 minutes, 95% CI: -1.46, -0.10) and the operating time (WMD -6.42 minutes, 95% CI: -6.95, -5.90) were slightly reduced during open access.
'Visual/open' versus 'hybrid visual/close'.
None of the included studies looked at open versus optical trocar access.
'Hybrid visual/close' versus 'blind/closed'.
Only one retrospective cohort study (with only 4 out of 100 patients operated on using optical trocar; quality score 17) and one grey literature abstract looked at optical trocar versus needle/trocar access; the data were inconclusive. None of the included studies looked at optical trocar versus direct trocar access.
'Blind/closed' methods: direct trocar versus needle/trocar access.
Three RCTs (quality score for all: 17) and 2 non-RCTs (quality score: 13 to 17) compared direct trocar with needle/trocar access. Further information was provided by 8 case series looking at direct trocear and 8 case series looking at needle/trocar access.
Safety: the data on major complications were inconclusive, whereas the minor complications reported in RCTs were fewer with direct trocar access (RR 0.19, 95% CI: 0.09, 0.40), predominantly owing to a reduction in extraperitoneal insufflation.
Efficacy: the pooled outcomes relating to the ability to establish pneumoperitoneum were inconsistent; information on the other efficacy outcomes was not reported.